Embodiments of the invention relates to an array substrate and the manufacturing method thereof.
TFT-LCDs (thin film transistor liquid crystal displays) are currently a mainstream flat panel display. A liquid crystal panel comprises an array substrate and a color filter substrate that are joined together face to face. According to the requirement of different structure designs, the circuit structures such as gate scanning lines, data lines, and common electrodes can be formed respectively on the array substrate and on the color filter substrate.
For a TFT-LCD of large size and high resolution, signal delay due to line resistance has serious an adverse effect on display quality. A way to solve the problem is to adopt a material of low resistance. The resistivity of an active metal is generally much lower than that of a non-active metal; for example, the active metal copper (Cu) has a resistivity of approximately 1.7×10−6 Ohm/centimeter (Ω/cm), while the non-active metal molybdenum (Mo) has a resistivity of approximately 5.7×10−6 Ω/cm; an active metal such as copper is therefore often used as the material for forming patterns on a substrate. Notwithstanding its relatively good conductivity, copper has a number of disadvantages, for example: 1) the adhesion between copper and a glass substrate or silicon nitride is poor; 2) when in contact with silicon nitride, copper is ready to diffuse, which adversely affects the insulating characteristics of silicon nitride, and copper can react with silicon to form copper silicide; and 3) copper may contaminate equipments in the subsequent process such PECVD (Plasma-Enhanced Chemical Vapor Deposition), which adversely affects film characteristics.
At present time, it is a regular approach to form a copper wiring structure of three layers: a lower barrier layer, a copper or copper alloy intermediate layer, and an upper barrier layer. Such an approach can reduce deterioration of TFT properties due to the diffusion of copper. However, the side surfaces of the copper wiring, not protected by any protection layer, are still exposed, which still has an adverse effect on the insulating material layer of silicon nitride.